Fluid pump and control



Jan. 3l, 1956 l.. T. sToYKE FLUID PUMP AND CONTROL.

4 Sheets-Sheet l Filed Dec:v l5, 1951 INI/EN TOR.

Jan. 3l, 1956 L.. T. s'roYKE 2,732,808

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Jan. 3l, 1956 L. T. STYKE FLUID PUMP AND CONTROL 4 Sheets-Sheet Z5 Filed Dec. 13, 1951 EEE-v \\\\\:J|.`Y\\7.. A @mwN &?/////v v @NN @N RWN mwN l@ Nl NIQQQNI www @N GN @mt s Nh. @uw m55@ 6N N @WSW @www N @N El ww w g :1. QS# C NWN mwN. h /ax 3 N mw NSN Mg m? @EN w @Z N hm @uw www www# @Qww w @QN Jan. 3l, 1956 1 T. STOYKE 2,732,803

FLUID PUMP AND CONTROL Filed Dec. 13, 1951 4 Sheets-Sheet 4 L idw' BVZM en, @my /e MM M @t pron) rom AND coNrnoL Ludwig T. Stoyke, Rockford, Ill., assigner to Sundstrand Machine Tool C0., a corporation of Illinois Application December 13, 1951, Serial N 261,454

11 Claims. (Cl. 103-173) This invention relates to pumps and more particularly to variable displacement multiple outlet fluid pumps.

It is the general object of this invention to produce a multiple outlet variable displacement pump of improved design and construction. l

It is a more specific object of this invention to produce control means for a variable displacement pump with the control means being adapted to vary the displacement of the pump in response to a control. l

Still another object of the invention is to produce a control device for a variable displacement pump in which variable control oil pressure is employed for controlling the displacement of the pump, with the control device including a servo-type valve mechanism so constructed as to provide for efficient operation thereof even at extremely low control fluid pressures.

A further object of the invention is to produce a control device for a multiple outlet fluid pump including means sensing the pressure in each outlet and operable upon the buildup of an excessive pressure in any one or more outlets to reduce the pump outlet pressure to substantially zero.

Still another object of the 'invention is to produce an outlet pressure sensing device of the type described in the preceding paragraph including means, which may take the form of a dashpot, or hydraulic follow-up mechanism, for stabilizing the iluid pressure by gradually regulating the movement of a pilot valve actuated by the sensing means in response to excessive pressure in any one or more outlets.

A further object of the invention is to produce a variable displacement pump which includes a valve chamber having a wheel-type `valve mounted therein for controlling the outlet ports and to provide in such a chamber a fixed port plate forming one wall thereof and so constructed and arranged as to present a plane porting face to the valve regardless of the outlet pressures existing in the chamber.

Yet another object of the invention is to -produce a port plate of the type described in the preceding paragraph which is provided with fluid passages so as to apply pump outlet pressure to both sides of the port plate to prevent Warpage under high outlet pressures.

Still another object of the invention is to produce a multiple outlet piston-type fluid pump which is provided with means for flushing the cylinders and pistons to prevent sticking of the pistons under all operating conditions.

Other and further objects of the invention will be readily apparent from the following description and drawings in which:

Fig. 1 is a longitudinal section through a uid pump housing and discharge manifold embodying the invention;

Fig. 2 is an enlarged detailed section of one portion of the valve chamber showing the valve plate, the port plate, and passages formed therein to prevent warpage of the plate;

VFig. 3 isa schematic diagram'ofthehydraulic circuit showing, in section, the pump and the relief, control relay and priming valves;

Fig. 4 is an enlarged detailed sectional view of the relief valve;

Fig. 5 is an enlarged detailed sectional view of the relay control valve and the priming valve; and

YFig. 6 is a plan view of the valve port plate.

While the invention is susceptible of various modifications and alternative constructions, it is herein shown and will hereinafter be described in its preferred embodiment. It is not intended, however, that the invention is to be limited thereby to the speciiic construction disclosed. On the contrary, it is intended to cover all modifications and alternative constructions falling Within the spirit and scope of the invention as defined in the appended claims.

Many of the features of this invention are improvements on the multiple outlet fluid pump and control shown and described Vin the copending application of Ludwig T. Stoyke, Serial No. 132,293, filed on December l0, 1949, now Patent No. 2,604,046.

Pump construction plurality of discharge ports 20 with one of the latter discharge ports being provided for each of the cylinders 13.

The cylinder `block is generally annular in form and is `provided with an vintegral flange 21 positioned between the casing sections 10 and 11 with the casing .sections being 'secured to each other and to the intervening flange by a plurality of bolts 22. The cylinder block is pro- `vided`with a cylindrical recess in its right-hand 'end (as Ashown in Fig. l) to form a cylindrical valve chamber 23 having opposed parallel faces 24 and 25 formed respectively by the end face of the cylinder block 12 andby an annularbronze insert 26 secured to a port plate 27 which, in turn, is secured to the casing by the bolts 22 through the medium of an integral flange 28,

The valve 13 is positioned with its annular rim portion 30 in vthe valve chamber V2.3 between the cylinder discharge ports 31 and the radially aligned outlet ports 20 lopposite thereto. The valve is given a gyratory movement by means of an eccentric pin 32 which is carried on a rotatable shaft 33 positioned in axial alignment with the shaft 16 and connected thereto by a spline arrangement 34. The valve 18 is freely rotatable about the pin 32 and is provided with a perforated valving `ri`rn,'the perforations being in the form of a plurality of openings 35, extending therethrough with the openings lbeing adapted to interconnect each of the cylinder` discharge ports lwith its opposed outlet port and to prevent cross-porting in the valve chamber. The particular type lof valve shown is more specifically described in the copending application of Ludwig T. Stoyke and Bruce H. Mosbacher, filed on December l0, 1949, as Serial -No. 132,292, now Patent No. 2,579,879. 4

The port plate 27 is held against a flange portion'36 bythe bolts 22 and is provided on the face abutting the portion 36 with an annular undercut portion forming a presz`sure balancing chamber'3'7. To provide a seal between the 'port plate27'and theendsect-ion-ll at the location of the pressure balancing chamber *37, lthere isprovideda sleeve 38 for each outlet port 20 positioned at such juncture and making fluid-tight engagement with the port plate and the casing through the medium of a plurality of O rings 39. l

It has been found that, under the extremely high pressures developed by the pump, steel port plates of even over one inch in thickness warp and thus permit leakage around the end faces of the valve 13. In order to avoid such warpage, means are provided for admitting outlet pressure to the pressure balancing chamber 37 to pressurize the back face of the port plate, which pressure counteracts the pressure on the valving face of the plate to minimize any bending thereof under stress. Accordingly, andl as best seen in Figs. 2 and 6, the port plate 27 and the bronze insert carried thereby are drilled to provide a plurality of openings 4t) each extending through the port plate and opening to the pressure balancing chamber 37. One of the passages 40 connects with a radial passage 41 which in turn is connected to an opening 42 through the port plate and insert and communicating with the valve chamber 23. The opening 42 is in free communication with the valve chamber 23 and balancing chamber 37 at all positions of the valve 18 therein while the valve chamber end of each of the passages 40 is, at all times, blocked olf by the end faces of the valve.

As the valve 18 is designed to oscillate within the valve chamber 23 formed between the recess in the end of the cylinder block and the face of the port plate within Welldefined clearances, a certain amount of leakage continuously exists between the high pressure and the low pressure areas of the valve. This leakage creates a pressure gradient across the Valving face. By locating the openings 40 in this region an average and substantially constant pressure is attained, which is applied to the balancing chamber 37 to balance the hydraulic pressure on the valving side of the port plate. As the leakage pressure is a function of Vthe average outlet pressure the port plate is never subject to an unbalanced load condition and thus is not subject to distortion and resulting inefficiency regardless of theI discharge pressure in each individual outlet port. As both the pressure balancing chamber 37 and the outer portion of the valve chamber 23 are sealed, very little flow of liquid is directed into these regions once they are filled. The normal pressure distribution between the valve and the port plate is unaffected and therefore the lluid displaced from the individual pistons is also unaffected so Vthat the ilow distribution remains unchanged within the limits of the volumetric efficiency of the pump and the v same quantity of fluid is delivered to each outlet port.

The bronze insert 26 is the wear surface in the valve chamber and is so constructed as to be replaceable Whenever required. In order to insure that the wear takes place on the insert, the cylinder discharge port plate is provided with an annular undercut portion 44 so as to pressurize the cylinder-port side of the valving rim and thus to urge the other side of the rim against the insert 26.

The shaft 16 is rotatably mounted within the casing on roller bearings 47 and ball bearings 48. A double seal indicated at 50 is provided at the left-hand end of the shaft (as seen in Fig. l) to prevent leakage from the interior of the casing into the driving means for the pump. In many forms of installation, it is contemplated that diesel oil may be used as the lubricant within the casing while ordinary lubricating oil will be provided for the driving mechanism for the pump. To prevent contamination of the lube oil by the diesel oil, the double seal 50 is provided which includes a sealing ring 51 urged into engagement with a carbon seal 52, fixed to the shaft 16, by a plurality of springs 53. A second rotating seal is provided between a sealing ring 54 on the shaft and a stationary seal 55 contacting the same. The carbon ring s 52 and the second sealing ring 54 are secured in fluidtight relationship to the drive shaft 16 by the O rings 55 as shown. A drain is provided for the space 56 between the two seals so that leakage in either direction through either seal may be drained therefrom, thereby preventing contamination `of one lubricatingmedium with the other.

The wobbler device 17 includes an inner ring member 60 which is pivotally mounted on the shaft 16 by means of a pin 61 extending therethrough. The wobbler includes an outer ring 62 carried on the inner ring by the antifriction thrust bearing 63 and roller bearing 64 and is arranged with a ilattened face positioned to engage the adjacent convex end of the pistons 14. It will be noted that the pin 61 about which the wobbler pivots is off-center with respect to the central longitudinal axis of the shaft 16 and with respect to the wobbler face. Thus as the shaft is rotated, an inertia load is applied to the wobbler tending to rotate it about the pivot to a position imparting maximum stroke to the pistons. This inertia load is augmented by the hydraulic load applied to the pistons, as will hereinafter be dscribed, and thus the wobbler tends to assume a position causing maximum stroke with rotation of the shaft.

To minimize vibration during operation of the pump at high speed, counterweights are provided on the shaft 16 and also on the eccentric shaft 32 to olset the inertia load applied by the off-center mounting of the wobbler and of the valve respectively. To this end, there is secured to one side of the drive shaft an arcuate counterweight 65, while another counterweight 66 is secured to the shaft 32. The respective counterweights are, of course, positioned oppositely the eccentricity they are to compensate for. Thus, the counterweight 66 is positioned oppositely of the valve shaft 32 while the counterweight 65 is positioned oppositely of the wobbler pin 61.

A plurality of springs 7u are located in a sleeve 72 positioned between the cylinder block and an outer stationary sleeve 76 mounted in the casing. These springs bear at one end against an annular collar 73 which ls supported on the cylinder block flange and serve to force the movable sleeve 72 against the outer bearing wobbler plate 62 to urge the wobbler to neutral position. By moving the sleeve 72 away from the wobbler against the compression of the springs, the wobbler is free to assume a stroke-imparting position as previously described. Hydraulic means are provided for so moving the sleeve to vary the position of the wobbler and hence the output of the pump. To this end, the sleeve is provided with a shoulder 74 forming, in effect, a piston. The piston is reciprocable in a chamber 75 formed between the sleeve 72 and the sleeve 76, the latter sleeve being secured in fluid-tight relationship to the casing 10 by a number of O rings 77. Introduction of uid under pressure into the chamber 75 serves to move the sleeve 72 against the compression of the springs to increase the wobbler angle while exhaust of lluid from the charnber permits the springs to move the wobbler toward neutral.

Each of the pistons 14 is provided with a relatively larger section adjacent its outer end and a relatively smaller section 81 adjacent its inner end and each cylinder 13 is similarly proportioned as to engage each of the sections of the piston. Such proportioning of the pistons provides an annular shoulder 82 on each piston to which fluid pressure is applied to move the pistons to the left on their intake strokes. For supplying the fluid pressure for moving the pistons on their intake strokes, there is provided a gear pump mounted upon `the shaft 33. Fuid is supplied to the pump 90 by an intake passage 91 and the discharge side of the pump is connected by means of a passage 92 to a groove 93 provided in each of the cylinders 13. The groove 93 is located at the innermost position the shoulder portion S2 attains under full piston stroke and -thus the pressure generated by the pump 90 serves constantly to urge the pistons toward the wobbler. The gear pump 9i) also serves as the source of iluid pressure for operating the control system hereinafter to be described.

As previously noted, the pump of this invention may be lused as a-fuel pump, and where'the fuel is Bunker C or #t6/fuel oil diiticulty `is apt to arise with deposits from the oil encrusting the pistons so as to cause the same to stick in the cylinders. To prevent such accumulation of deposits on the pistons, the vpump of this invention is designed to accommodate any one of several iiushing systems in order to provide means for constantiy cleaning the pistons during operation of Vthe pump. To this end, there is provided a passage95 for each cylinder which opens to the pump intake 19 and connects by means of a second passage 96 to an annuiar relier groove 99 around each cylinder 13 intermediate the location of the annular groove 92 and the discharge end of the cylinders. A second passage 97 also connects each annular groove 99 to an additional passage 98 which opens exteriorly of the casing. The pump inlet end of the passage 95 and the exterior ends of the passage 9d are threaded so that either may be closed by a plug, depending upon the type of flushing system employed. In one such system, the passage 9S may be connected, by means of its threaded end, to an exterior source orc solvent under pressure and with passageway 9S blocked, the solvent may be conducted to the groove 99 in each of the cylinders 13 so that solvent hows along the pistons (by virtue of piston clearances) constantly to dissolve any deposits of contaminating material sticking to the pistons and to wash such dissolved deposits into the fuel'inlet. As long as the pressure of the solvent is higher than fuel pressure this flushing system maybe used. lf such solvent pressure is not available a second annular relief groove 99a may be located between the chamber 93 and groove 99. By maintaining a solvent pressure less than control oil pressure, the solvent is always directed to the fuel inlet along the piston clearances into the annular relief groove 99 and thence passes through passageways 96 and 95 to vthe inlet 19. By circulating solvent, which may be the fuel itself, through the piston clearances deposits are frequently prevented from forming on'the cylinder and piston Walls. This circulation is achieved by blocking the end of the passage 93 and thus directing the fuel leakage through the clearances and into the passage 96 and iinally into the pump inlet. if it is desired, under the last mentioned conditions to prevent ushing into the intake, the intake end of the passage 95 may be closed by a plug and the passage 93 connected to a drain so that the flushing of the fuel is into the passage 97 and thence to a point exterior of the casing. lf, in the latter system, the plug be removed from the intake end of the passage 95, fuel under inlet pressure is added to the fuel leaking past the pistons thereby considerably increasing the scouring action to remove deposits, ail of which may be removed to a point exterior of the casing through the passage 98.

Any of the foregoing liushing systems may be used as operation of the pump requires.

In the particular embodiment illustrated, eighteen pistons are provided in the pump which discharge into an vequal number of discharge ports 20. The end cap 11 is provided with a manifold arrangement 1d@ designed to combine the eighteen discharge ports into six separate outlets by joining three ports equally spaced in the discharge port circle to form six groups of three discharge ports each. To this end, the manifold is provided with six annular grooves 1M separated by D rings 1132. Slots 103 are milled in Vthe manifold to connect each discharge port 2d to one of the six annular grooves 101. Six discharge outlets 164%199 (Fig. 3) are provided, each connected to one of the slots 103.

Main relay control valve Direct control of the displacement of the pump is achieved through a main relay control valve 110 which may be mounted directly on the pump casing. The relay control valve includes a bore 111 connected by means of a passage 112 'to the annular grooves 93 which are constantly supplied with oil under pressure from the pump 90. As previously noted, this pressure is utilized to return the pistons on their intake stroke and is piloted off to the main relay control valve bore. The main relay control valve is provided to direct pressure into the chamber 75 to move the sleeve 72 away from the wobbler against the pressure of the springs. Thus as increased pressure is directed into the chamber 75 by the relay control valve, the springs 7 d are further compressed to permit the wobbler to assume a greater stroke imparting position. Conversely as iuid is valved out of the chamber 75 by the relay control valve, the springs serve to move the sleeve toward the wobbler to tilt the wobbler towards its neutral or nonstroke imparting position.

Referring now to Fig. 5, it will be noted that the right'- hand end of the bore 111 is enlarged at 113 to accommodate e sleeve 114 provided with a portion 115 extending into the bore 111, with the portion of the sleeve within the bore 113 being slightly spaced therefrom as to provide a chamber therearound. Reciprocably mounted within the sleeve 114 is a piston 116 constantly urged in the direction of the main bore 111 by a spring 117.

Slidably mounted in the main bore 111 is a valving sleeve 118 provided with a port 119 which connects with an annular groove 121i formed in the outer surface of the sleeve and so proportioned as to be constantly in communication with a passage 121 which ultimately connects with the chamber 75, through the medium of a relief valve to be hereafter described, to control the sleeve.

The port 119 is controlled by a land 122 formed at one end of a spool-type valve 123 which is slidably mounted within the sleeve 113. The other end of the valve 123 is connected to the piston 116 to be moved therewith. Also connected to the piston 116 is a rod 125 which extends through the center of the spool valve and is connected to a piston 126 reciprocably mounted in the end of the bore 1i 1 opposite the piston 116. In said opposite end of the bore there is provided a spring 127 which has one end bearing against the piston 126 and its other end bearing against a stop member 128. Means in the form of a screw device 129 is provided for adjusting the tension of the spring 127.

Secured to one end of the sleeve 118 is a stop member 13@ against which the upper bifurcated end of a followup member 131 may bear. The member 131 is pivotally mounted at 132 intermediate its ends Withthe lower end 133 thereof bearing against the sleeve 72 so as tor be moved with movement of the Wobbler. The rod is provided with a stop collar 134 adapted to contact the stop 13d with movement of the Vvalve 123 in one direction or to contact a second stop 135 fixed to the sleeve with movement of the valve in the other direction. The stops 131i, 13d and 135 are so positioned as to limit valve travel independently of movement of the sleeve to .030 inch.

Communicating with the space between the enlarged portion 113 of the bore and the sleeve 114 is a control uid passageway 136. This passageway is adapted to be connected to a control oil pressure system so that manual control of the pump may be eifected. Thus as oil under pressure is introduced through the passage 136 .into the bore 113 such pressure serves to move the piston 116 and hence the spool valve 123 to the left (as seen in Fig. 5f) moving the tand 122 to open'the port 119 (within the limits of permitted valve travel) to permit oil under pressure from the gear pump 90 to be directed from the passage 112 into the passage .121 to increase the displacement of the pump. As the springs within the sleeve are compressed and the sleeve 72 moves to the right, the lower end 133 of the follow-up member -131 also moves to the right. As long as the maximum compression of the control spring 127 for a given control oil pressure has not been obtained, the control pressure causes the pilot piston 123 to travela greater distance than the p ilot sleeve 118 actu- 'ated by the follow-up arm. Once maximum compression of spring 127 is obtained the pilot piston remains stationary and further movement of the wobbler into stroke position reduces the valve opening to establish a sleeve pressure in the chamber 75 balancing the hydraulic and inertia moment applied on the wobbler. As the displacement of the follow-up arm is a direct function of the delivery of the pump, the control pressure applied in chamber 113 is also thus related. Therefore the pump delivery within its capacity rating may increase in direct ratio to the control oil pressure. Should the wobbler overshoot the position of equilibrium, the follow-up arm shifts sleeve 1153 slightlyto the left in a follow-up manner to expose the port 119 to case pressure so that the sleeve springs 7i? reduce the pump stroke. Should it be desired to reduce the pump displacement, the control oil pressure is reduced permitting the piston 116 to move to the right under the influence of the spring 127, thus moving the land 122 to 4the right of the port 119 permitting oil in the chambers 75 to be drained through that port and a drain port 137 in the sleeve and thence through the passage 133 through which the follow-up member extends into the interior of the pump casing. As the sleeve 72 moves to the left under the influence of the springs 7i), the follow-up member is pivoted in a clockwise manner again to move the sleeve towards the land to bring the land into registry with the port 119, halting further movement as described.

When control oil pressures are between 40 and 22() lbs. p. s. i., there is no need for the spring 117, inasmuch as all of the parts of the control valve will remain in proper position at those pressures. When a long oil return line is employed, back pressure in the pump casing is created and where the control oil system is designed to operate at a low pressure, for example as low as lbs. p. s. i., the spring 117 has been found necessary to provide slight additional pressure against the piston 116 to maintain all of vthe parts of the relay valve against separation. Thus, the

spring 117 may be included or omitted as the operating conditions require.

Associated with the relay control valve is a priming valve assembly 140 which is connected to the variable control oil chamber by means of a passage 141. The priming valve is provided with a bore 142 having an inlet chamber 142:1 into which variable control pressure is directed. Air in the variable control oil system is readily passed through an orifice 143 and through an exhaust passage 144 without moving the piston 145 within the bore and against the tension of the spring Je. When air has been exhausted from the system, the pressure drop across the orifice creates sufficient bach pressure to move the piston 145 to a position where communication between the orifice 143 and exhaust ports 1417 is cut off, thus allowing control oil pressure to build up in the bore 113.

To balance the control to case pressure, the bore in which the piston 126 is reciprocable is connected 'oy means of a passage 143 to a drain passage 149. The passage 149 connects, by means of auxiliary passage 149er, to the space 56 between the double seals on the drive shaft, to permit drainage of control oil leaking past the piston 126 and oil leaking through either of the double seals.

Outlet pressure relief valve The particular embodiment of the invention shown in the drawing is admirably suited for use with a turbine engine having six jets with each of the outlets Mia-169 connected to an individual jet for supplying fuel thereto. In order to safeguard the pump and fuel system of such -an engine, it has been found desirable to incorporate an and the fuel system to excessive pressure. To effect such control of the outlet pressure, there is provided an outlet pressure relief valve 15@ (see Fig. 4) which includes a casing 151 provided with an elongated bore 152 therein. A plurality of sleeves 153 are spaced from each other along the bore with the space between adjacent sleeves providing means of communication between the outlets from the pump and the passages to the turbine jets. For convenience, the latter passages have been given the same reference numerals as the corresponding pump outlets with the let r a added. Thus, the outlet 165 is connected to the passage 165e through the bore 152 in the space between adjoining sleeves 153.

Reciprocably positioned in each sleeve is a piston-like member 154 each provided with a reduced portion 155 at one end which bears against the base 156 of the next adjacent piston-like member. With the reduced portions each permitting fuel to ow from a pump outlet to its corresponding jet connection, it will be noted that each piston is subjected at each end to the outlet pressure in adjoining outlets. The reduced portion 155a on the rightrnost piston-like member bears against one end 157 of a valve 153 slidable in the right-hand portion 159 of the bore. The valve 158 is provided with two tapered lands 161B and 161 which control respectively passages 152 and'163 formed in an insert 16d iitted in fluid-tight engagement into an enlarged bore 165 aligned with the bore 152. The passage 162 is connected to the passage 121 leading rom the relay valve while the passage 163 connects with another passage 156 which in turn is connected with the chamber 75.

The relief valve 15G is illustrated in its normal position, affording free communication between the passages 162 and 163 and, hence, between the passages 121 and 166 so that movement of the relay valve in response to variations in control oil pressure serves directly to shift the sleeve to effect a change in the wobbler angle. The

valve 153 is also movable in response to pressure buildups in any one of the outlets. To prevent movement of the valve 15S under normal operating conditions, there is provided a spring 17d which bears against a thrust member 171 which irl/turn bears against a pin 172 integrally connected to a hydraulic follow-up or dashpot-type piston 173 slidable in a step cylinder 174 formed in the insert 164. The opposite side of the piston 174 is formed into a push rod 175 which bears against the valve 158. Suitable drain channels 175 are provided which connect into an annular groove 177 in turn connected to a drain connection 178 to take care of any leakage past the valves and pistons. The space between a sleeve cap 171 and the piston 173 forms a chamber 18% which is maintained filled with duid at the pressure in sleeve chamber 75, and the outer surface of the piston is provided with a spiral groove 182 so that a restricted passageway is provided for the oil moved from one side of the piston to the other. A channel 164 formed in the insert 164 connects at one end to the conduit 166 and at the other end to a chamber 185 to supply oil at sleeve pressure to that chamber and, through the groove 182, to the chamber 180. An orifice 133 is located in channel 184 to restrict the oil flow from chamber 185 when the spring 170 moves the piston 173 from right to left (as seen in Fig. 4).

From the foregoing, it is believed to be apparent that should the pressure in any one outlet exceed the preload of spring 170, the effect of such pressure is to tilt the wobbler toward neutral position. Assuming, for example, that the nozzle connected to the passage 109a becomes clogged, the resulting buildup in pressure in the annular space between the piston-like members 15411 and 154b urges the valve 158 and the piston 173 to the right against the compression of the spring 170. Because uid must flow along the groove 182 of the piston 173, movement is slowed somewhat, but is continued until the land 16) blocks the passage 162 while the land 161 is moved sufficiently to establish communication between the passage 163 and one of the drain passages 176. When Athis condition has been attained, the pressure of the fluid in the chamber 75 is greatly reduced and simultaneously that chamber is placed in communication with the ydrain so as to permit the fluid to be expelled therefrom by the action of the springs, thus shifting the wobbler towards neutral position. It will be noted that the outlet `pressure relief valve is so incorporated into the control system as to exercise direct control over the wobbler independently of th'e relay control valve or the variable control oil pres,- sure. rthus a more direct and positive control over the wobbler is attained.

To prevent a sudden change in movement of the valving piston 158 which drops the pressure and drains the uid from the chamber 75 allowing the springs to return the Wobbler to neutral and reducing the fuel pressure below the fuel relay valve setting quickly so that the spring 170 will tend to restore the position of the valving piston 158 to close the drain channel 176 and open the pressure port 162 to shift the wobbler into stroke position again increasing the fuel pressure, the restricting orifice 183 is provided on the intake channel to chamber l185 and the groove 182 is provided on the piston 174. A sudden change increasing fuel pressure thereby causes `only a gradual change in valve movement as the pressure is built up in chamber 180 producing a retarding force resulting from the oil being forced through the groove on the piston. Similarly a sudden drop in fuel pressure causes the spring 170 to shift the piston 158 to increase the fuel delivery by increasing the stroke position of the wobbler. However, pressure is built up in chamber 185 creating an opposing force to the spring force by restricting the oil ilow through the orifice 183 from the chamber 185. In this manner a hydraulic follow-up mechanism is provided to maintain stability of fuel flow at all times when regulated by the overpressure relief valve.

Ir" desired, the space between the rightmost piston-like member 15417 and the valve 158 may be connected by means of the conduit 187 to the pump intake again t0 provide for flushing of the bore 151. Thus, fuel leaking past each of the piston-like members is reintroduced into the pump intake to reduce the possibility of buildup of waxy or other deposits on the piston-like members which might result in their sticking.

I claim:

l. In a uid pump having an inlet, an outlet, a cylindrical valve chamber having parallel end faces, a port in one of the end faces connected to the discharge side of the pump, a port in the other end face connected to the pump outlet and a wheel-like valve in the chamber having a valving rim in substantial duid-tight sliding engagement with the end faces and eccentrically movable in the chamber to connect the discharge port alternately with the inlet and with the outlet port, said valve having a diameter smaller than the diameter of the valving chamber and defining with the valving chamber an annular space around the periphery thereof, means for preventing' distortion of the chamber comprising an outlet port plate having one side forming one of said endvfaces, means defining a pressure balancing chamber includingthe other side of the outlet port plate, an opening in said annular space in constant communication with the pressure balancing chamber and a plurality of openings in the port plate and positioned in an annularY rowhaving a diameter less than the outerl diameter of the valving rim and constantly covered by said valving rim with each of said plurality of openings being connected to said pressure balancing chamber to subject said other side of the port plate tothe leakage pressure across said valving rim with said leakage pressure substantially equaling the average pressure applied to the first mentioned side of the outlet port plate.

2. A fluid pump having a casing, a wobbler, a plurality of annularly arranged cylinders in the' easing, a piston in each cylinder, means for causing relative rotation between the wobbler and the cylinders toiov the pistons through gagement with the Vend faces, means for driving the ,valve through an eccentric movement to connect the discharge ports alternately to the inlet and to the` outlet, a flushing passage connected at one end to the cylinders intermediate the ends thereof and at the other end of the valve chamber, a second flushing passage connected at one endv to the cylinders intermediate the ends thereof with the other end of the second passage opening to the exterior 'of the casing, and means for connecting the exterior end of the -second passage to a source of solvent.

3. A fluid pump having a casing, a wobbl'er, a plurality of annularly arranged cylinders in the casing, a piston in each cylinder, means for causing relative rotation between the wobbler and the cylinders 'to move the pistons through a pumping stroke, an inlet and outlet for the pump, a flushing passage connected at one end to the cylinders intermediate the ends thereof and at the'other end to the inlet, a second flushing passage connected at one end to the cylinders intermediate the ends thereof with the other end of the second passage opening to the exterior of the casing, and means for connecting the exterior end of the second passage to a source of solvent.

4. Control means for a multiple outlet variable displacement pump comprising lluid operated means for controlling pump displacement, a source of operating fluid under pressure to operate the control means, an outlet pressure relief valve having a bore, a plurality of piston-like members with each member having a portion in fluid-tight sliding engagement with the bore and a reduced portion in contact with another member to provide a space between adjacent members, means connecting each outlet of the pump with the bore at said spaces to subject each pistonlike member to the opposed pressure in two outlets, resilient means holding the members against movement in the bore under normal operating outlet pres-sure and yieldable under excessive pressure in any outlet to permit sliding movement of any member subjected thereto, a control valve in said bore intermediate the resilient mean-s and the adjacent piston-like member and movable with movement of any member, fluid passage means controlled by the valve and connected to said source and tosaid displacement control means whereby movement of the valve in response to movement of any member operates to control the liuid pressure to decrease pump displacement, and a dashpot connected to the control valve for damping movement thereof in response to changes of pressure in said spaces.

5. Control means for a multiple outlet variable displacement pump comprising fluid operated means for controlling pump displacement,a source of operating fluid under pressure, control means interconnecting the source and the displacement control means, said control means including a relay valve slidable in a bore and movable in response to a control pressure to direct operating fluid to the displacement control means to control displacement of the pump, an outlet pressure relief vaive having a bore, a plurality of piston-like members with each member having a portion in duid-tight sliding engagement with the last named bere and a reduced portion in contact with another member to provide a space between the .first portions of adjacent members, means connecting each outlet with the relief valve bore at said spaces to subject each, member to the opposed pressure in two outlets, a relief valve slidable in the relief valve bore and contacting one of the members, a spring contacting the valve to hold the members and valve against movement under normal operating outlet pressure and yieldable under excessive pressure in any outlet to permit sliding movement of a member subjected thereto'to cause movement of the relief valve, a pair of ports in the relief of the relay valve.

f 11 valve bore Ycontrolled by the' relief va1ve,rmeans connecting the source of operating fluid with one of said ports, and means connecting the other of said ports with the bore 6. Control means for a multiple outlet variable displacement pump comprising fluid operated means for controlling pump displacement, a ,source of operating uid under pressure, control means interconnecting the source and the displacement control means, said control means including a relay valve slidable in a bore and movable in response to a control pressure to direct operating uid to the displacement control means to control displacement of the pump, an outlet pressure relief valve having aV bore, a plurality of piston-like members with each member having a portion in duid-tight sliding engagement with the last, named bore and a reduced portion in contact with another member to provide a space between the first portions of adjacent members, means connecting each outlet with the relief valve bore at said space to subject each member to the opposed pressure in two outlets, a relief valve slidable in the relief valve bore and contacting one of the members, a spring contacting the valve to hold the members and valve against movement under normal operating outlet pressure and yieldable under excessive pressure in any outlet to permit sliding movement of a member subjected thereto to cause sliding movement of the relief valve, a pair of ports in the relief valve bore controlled by the relief valve, means connecting the source of operating yfluid with one of the ports, means connecting the other port with the bore of the relay valve, and means connected to the relief valve for damping movement thereof in response to change of pressure in said spaces.

7. Control means for a multiple outlet variable displacement pump comprising means biasing the pump toward zero displacement, fluid operated means opposing the biasing means and operating to increase the displacement of the pump, an outlet pressure relief valve having a bore, a plurality of piston-like members with each member having a portion in Huid-tight sliding engagement with the bore and a reduced portion in contact with another member to provide a space between the first portions of adjacent members, `means connecting each outlet with the bore at said spaces to subject each member to the opposed pressure in two outlets, a spring holding the members against movement in the bore under normal operating outlet pressure and yieldable under excessive pressure in any outlet to permit sliding movement of a member subjected thereto, a source of control fluid under pressure, a source of operating fluid under pressure, a relay valve connected to the source of operating fluid, said relay valve having a control iluid chamber, a bore, and a valving member movable in thebore in response to increasing control fluid pressure in the chamber to direct operating uid to the opposing means to increase pump displacement and said valving member being movable in response to decreasing control fluid pressure in the chamber to tank operating fluid from the opposingr means, a passage connecting the source of operating fluid to one end of the relief valve bore, a second passage connecting said end of the bore to the bore of the relay valve, a third passage connecting said end of the bore to a drain, and a control valve in said end of the bore, said control valve being in contact with a piston-like member and movable therewith to control the passages.

8. Control means for a multiple outlet variable displacement pump comprising means biasing the pump toward zero displacement, fluid operated means opposing the biasing means and operating to increase the displacement of the pump, an outlet pressure relief valve having a bore, a plurality of piston-like members with each member having a portion in fluid-tight sliding engagement with the bore and a reduced portion in contact with another member to provide a space between the rst portions of adjacent members, means connecting each outlet y ,with the bore at said spaces to subject each member to the opposed pressure in two outlets, a spring holding the members against movement in the bore under normal operating outlet pressure and yieldable under excessive pressure in any outlet to permit sliding movement of a member subjected thereto, a source of control fluid under pressure, a source of operating .fluid under pressure, a relay valve connected to the source of operating fluid, said relay valve having a control fluid chamber, a bore, and a valving member movable in the bore in response to increasing control fluid pressure in the chamber to direct operating fluid to the opposing means to increase pump displacement and said valving member being movable in response to decreasing control fluid pressure in the chamber to tank operating iiuid from the opposing means, a passage connecting the source of operating fluid to one end of the relief valve bore, a second passage connecting said end of thebore to the bore of the relay valve, a third passage connecting said end of the bore Vto a drain, a control valve in saidendV of the bore, said control valve being in contact with a piston-like member and movable therewith to control the passage, and a dashpot connected to the relief valve' for damping movement thereof in response to changes of pressure in said spaces, the dashpot including a cylinder adapted to contain a hydraulic fluid and a piston in the cylinder and provided with a plurality of spiral grooves on its sidewalls to provide restricted passages for hydraulic'uid from one side to the other side of the piston.

9. Control means for a multiple outlet variable displacement pump comprising fluid operated means for controlling pump displacement, a source of operating uid under pressure, control means interconnecting the source and the displacement control means, said control means including a relay valve slidable in a bore, a control chamber in one end of the bore, a control pressure passage connected to the chamber, a piston in the chamber connected to the relay valve and movable in response to control pressure, a compression spring in the chamber and bearing against the piston therein with said spring operating in parallel with the control pressure, a second spring in the other end of the relay valve bore acting in opposition to the compression spring, said relay valve being movable in response to changes-in control pressure to direct operating fluid to the displacement control means to control displacement of the pump, an outlet pressure relief valve Vhaving a bore, Va plurality of piston-like members with each member having a portion in fluid-tight sliding engagement with the last named bore and a reduced portion in contact with another member to provide a space between the rst portions of adjacent members, means connecting each outlet with the relief valve bore at said spaces to subject each member to the opposed pressure in two outlets, a relief valve slidable in the relief valve bore and contacting one of the members, a spring contacting the valve to hold the members and valve against movement under normal operating outlet pressure and yieldable under excessive pressure in any outlet to permit sliding movement of a member subjected thereto to cause movement of the relief valve, a pair of ports in the relief valve bore controlled by the relief valve, means connecting the source of operating fluid with one of said ports, and means connecting the other of said ports with the bore of the relay valve.

10. A fluid pump having a wobbler, a plurality of cylfinders, a piston in each cylinder, means for causing relalet manifold secured to the plate and having a plurality of ports with each manifold port being aligned with a different one of the outlet ports, a plurality of sleeves each secured in Huid-tight relationship to the plate and to the manifold and interconnecting each outlet port with its aligned manifold port, a wheel-like valve having a valving rim in substantial iluid-tight sliding engagement with the end faces, means for driving the valve through an eccentric movement to connect each discharge port alternately to the inlet and to its associated outlet port, an annular pressure chamber between the plate and the manifold and through which the sleeves extend, and a plurality of passages in said plate arranged in an annular row and connecting the pressure chamber with the valve chamber, said row having a diameter less than the diameter of the valving rim and constantly covered by said rim to subject said passages and the pressure chamber to leakage pressure across said valving rim, thereby to subject both sides of the plate to the pressure of fluid in the valve chamber.

1l. A fluid pump having a wobbler, a plurality of cylinders, a piston in each cylinder, means for causing relative rotation between the wobbler and the cylinders to move the pistons through a pumping stroke, a cylindrical valve chamber, a discharge port for each cylinder opening into the chamber in an annular row, means forming a ilat end face of the chamber and through which the discharge ports extend, a plate having a flat face on one side thereof forming the other enti face of the chamber, a plurality of outlet ports in the plate arranged in an annular row, an inlet opening into the valve chamber, a wheel-like valve having a valving rim in substantial fluid-tight sliding engagement with the end faces, means for driving the valve through an eccentric movement to connect each discharge port alternately to the inlet and to its associated outlet port, a pressure chamber on the other side of the plate, and a plurality of passages extending through the plate and opening into the valve chamber at points constantly covered by the valving rim to subject the pressure chamber to leakage pressure across said valving rim, thereby to subject both sides of the plate to the pressure of uid in the valve chamber.

References Cited in the le of this patent UNITED STATES PATENTS 2,307,041 Hawley Ian. 5, 1943 2,397,314 Grosser Mar. 26, 1946 2,406,138 Ferris et al Aug. 20, 1946 2,579,879 Stoyke et al Dec. 25, 1951 2,604,046 Stoyke July 22, 1952 

